It's all a matter of conditioning, and intuitive motion.
I myself am quite ambidextrous (except my left handed writing is not particularly good). I am also left eye dominant, so most visual task are preferred with my LEFT eye -converse to what is normal for a right handed person.
If you are similarly ambidextrous, transitioning and readjustment to a "foreign" cockpit layout is genuinely not a problem. For instance, I learnt to fly on Piper Tomahawks - conventional layout - yoke in left hand, throttle in right hand. I then did a LOT of flying in the DeHavilland Tiger Moth, where the throttle is on the LEFT, and the stick in between your legs. You flew with your RIGHT hand, and throttle in your left hand. I found NO PROBLEM adjusting to it whatsoever - if anything, it was INCREDIBLY natural (I am sure all pilots would find this, especially fighter pilots that still have this layout today).
I similarly have NO difficulty whatsoever with the side stick ala Airbus. It's just as natural as a yoke, or even a centre stick ala Tiger Moth.
So, I honestly do not believe that a lefty should have any trouble in any cockpit layout to be perfectly honest, unless he/she had potentially poor pshychomotor skills / coordination.